Method and system for correcting image position based upon predetermined pattern portions

Abstract

An optical character recognition method and system adjusts positional, rotational and scaling differences between an input form image and a standard form image based upon selected corresponding portions of the two images prior to optically recognizing characters in predetermined areas of the input form. The corresponding portions include a predetermined mark such as a cross-line portions and or predetermined characters, and a selection process of these corresponding portions eliminates unlikely pairs of the corresponding portions based upon a distribution histogram analysis.

What is claimed is: 
     
       1. A method of identifying a crossed portion of lines in an image input which are represented by pixels, comprising the steps of: a) moving a mask consisting of at least five positionally fixed pixels against the image input, at least one of said five pixels located substantially at a center of other four of said five pixels, said one pixel being defined as a center pixel while said four pixels being defined as peripheral pixels;   b) modifying a pixel in the image input corresponding to said center pixel when any one pixel in the image input corresponding to said peripheral pixels has a pixel value other than a predetermined value; and   c) repeating said steps a) and b) until the crossed portion of the lines is surrounded by off pixels, the crossed portion being defined as an area where two lines cross in a substantially perpendicular manner.   
     
     
       2. The method of identifying a crossed portion of lines according to claim 1 wherein said step b) turns off the pixel in the image input corresponding to said center pixel when any one pixel in the image input corresponding to said peripheral pixels is originally turned on. 
     
     
       3. The method of identifying a crossed portion of lines according to claim 1 wherein said mask includes four of said peripheral pixels located each located at a corner of a rectangle. 
     
     
       4. The method of identifying a crossed portion of lines according to claim 1 wherein said mask includes four of said peripheral pixels located each located at a corner of a square. 
     
     
       5. The method of identifying a crossed portion of lines according to claim 4 wherein said peripheral pixels are located with each other at a distance of a multiple of eight pixels. 
     
     
       6. The method of identifying a crossed portion of lines according to claim 1 further comprising an additional step d) of confirming the crossed portion based upon a predetermined height and a predetermined width. 
     
     
       7. The method of identifying a crossed portion of lines according to claim 6 further comprising an additional step e) of determining a center of the crossed portion. 
     
     
       8. A system for identifying a crossed portion of lines in an image input which are represented by pixels, comprising: an input buffer for holding the image input;   a mask consisting of at least five positionally fixed pixels against the image input, at least one of said five pixels located substantially at a center of other four of said five pixels, said one pixel being defined as a center pixel while said four pixels being defined as peripheral pixels;   a cross line processor connected to said input buffer for modifying a pixel in the image input corresponding to said center pixel when any one pixel in the image input corresponding to said peripheral pixels has a pixel value other than a predetermined value until the crossed portion of the lines is surrounded by off pixels, the crossed portion being defined as an area where two lines cross in a substantially perpendicular manner.   
     
     
       9. The system for identifying a crossed portion of lines according to claim 8 wherein said cross line processor turns off the pixel in the image input corresponding to said center pixel when any one pixel in the image input corresponding to said peripheral pixels is originally turned on. 
     
     
       10. The system for identifying a crossed portion of lines according to claim 8 wherein said mask includes four of said peripheral pixels located each located at a corner of a rectangle. 
     
     
       11. The system for identifying a crossed portion of lines according to claim 8 wherein said mask includes four of said peripheral pixels located each located at a corner of a square. 
     
     
       12. The system for identifying a crossed portion of lines according to claim 11 wherein said peripheral pixels are located with each other at a distance of a multiple of eight pixels. 
     
     
       13. The system for identifying a crossed portion of lines according to claim 8 further comprising a cross line confirming unit for confirming the crossed portion based upon a predetermined height and a predetermined width. 
     
     
       14. The system for identifying a crossed portion of lines according to claim 13 wherein said cross line processor determines a center of the crossed portion. 
     
     
       15. A computer readable recording medium containing software for identifying corresponding positions in an image input which are represented by pixels, comprising the steps of: q) moving a mask consisting of at least five positionally fixed pixels against the image input, at least one of said five pixels located substantially at a center of other four of said five pixels, said one pixel being defined as a center pixel while said four pixels being defined as peripheral pixels;   r) modifying a pixel in the image input corresponding to said center pixel when any one pixel in the image input corresponding to said peripheral pixels has a pixel value other than a predetermined value; and   s) repeating said steps a) and b) until he crossed portion of the lines is surrounded by off pixels, the crossed portion being defined as an area where two lines cross in a substantially perpendicular manner.